By Ethan Covey
Bivalent, mRNA, COVID-19 booster vaccines provide protection against omicron XBB-related SARS-CoV-2 lineages, according to early estimates of national pharmacy testing data.
Data from the Increasing Community Access to Testing pharmacy testing program were used to estimate the effectiveness of updated COVID-19 vaccines against illness caused by omicron XBB/XBB.1.5 compared with BA.5-related variants in adults between Dec. 1, 2022, and Jan. 13, 2023 (MMWR Morb Mortal Wkly Rep 2023;72:119-124).
Investigators analyzed more than 29,000 nucleic acid amplification tests with spike gene (S-gene) amplification (SGTF) or S-gene target presence (SGTP) results available from adults who had previously received two to four monovalent COVID-19 vaccine doses. They used reduction or failure of SGTF in real-time reverse transcription–polymerase chain reaction as a proxy indicator of infection with likely BA.5-related sublineages and SGTP as a proxy indicator of infection with likely XBB/XBB.1.5-related sublineages.
The investigators found that the bivalent booster had a relative vaccine effectiveness of 52% against symptomatic BA.5 infection and 48% against symptomatic XBB/XBB.1.5 infection, when administered two to three months previously, compared with patients who did not receive a bivalent booster.
In all age groups (18-49, 50-64 and >65 years), the investigators found that vaccine effectiveness was similar against both BA.5- and XBB/XBB.1.5-related infections.
The investigators noted at the beginning of the study period, 13% of specimens that were sequenced nationwide were BA.2 sublineages, including 2.4% XBB.1.5 (95% CI, 0.6%-6.2%) and 5% XBB (95% CI, 3.7%-6.6%). By the end of the study period, BA.2 sublineages accounted for approximately 41%, including 37.2% XBB.1.5 (95% prediction interval [PI], 26.8%-49%) and 4% XBB (95% PI, 3.3%-4.7%).
Although concerns have arisen that bivalent booster doses offer lower neutralizing activity against XBB compared with other omicron sublineages, the study found that the updated vaccines helped protect against illness associated with omicron XBB/XBB.1.5-related variants for at least the first three months after vaccination among adults who had previously received two to four doses of the monovalent COVID-19 vaccine.
“Since updated, bivalent COVID-19 vaccines were authorized and recommended for use in early September 2022, CDC has used multiple strategies to monitor how well these vaccines are working in real-world conditions,” Ruth Link-Gelles, PhD, a doctoral epidemiologist at the CDC’s National Center for Immunization and Respiratory Diseases, in Atlanta, told Infectious Disease Special Edition. “This study adds to previous evidence indicating these updated vaccines are protecting people against the latest COVID-19 variants.”
Dr. Link-Gelles added that the CDC will continue to monitor vaccine effectiveness over time and as new variants emerge.
In the meantime, she advised people to stay up-to-date with recommended COVID-19 vaccines, including receiving an updated, bivalent COVID-19 vaccine when eligible.
“This is particularly true for older people and those with underlying conditions who are at higher risk,” she noted.
Dr. Link-Gelles reported no relevant financial disclosures.
